This invention relates in general to solenoid coils and in particular to a self-fusing solenoid coil.
An Anti-lock Brake System (ABS) is often included as standard or optional equipment on new vehicles. When actuated, the ABS is operative to control the operation of some or all of the vehicle wheel brakes. A typical ABS includes a plurality of solenoid valves mounted within a control valve body and connected to the vehicle hydraulic brake system. Usually, a separate hydraulic source, such as a motor driven pump, is included in the ABS for reapplying hydraulic pressure to the controlled wheels during an ABS braking cycle. An ABS further includes an electronic control module which is electrically connected to the pump motor, a plurality of solenoid coils associated with the solenoid valves, and wheel speed sensors for monitoring the speed and deceleration of the controlled wheels. The electronic control module is typically mounted upon the control valve body. The assembled control valve body, motor and control module form a compact unit which is often referred to as an ABS control valve.
During vehicle operation, the ABS control module continuously receives wheel speed signals from the wheel speed sensors. The control module monitors the wheel speed signals for potential wheel lock-up conditions. When the vehicle brakes are applied and the control module senses an impending wheel lock-up condition, the control module is operative to actuate the pump motor and selectively operate the solenoid valves in the control valve to cyclically relieve and reapply hydraulic pressure to the controlled wheel brakes. The hydraulic pressure applied to the controlled wheel brakes is adjusted by the operation of the solenoid valves to limit wheel slippage to a safe level while continuing to produce adequate brake torque to decelerate the vehicle.
Typically, the solenoid valves are operated intermittently. This not only reduces the power demand of the ABS, but also allows use of smaller sized components.